The present invention relates generally to fiber optic connectors and associated guide pin retention mechanisms and, more particularly, to a fiber optic connector having a ferrule that is compatible with conventional connectors and a variety of ferrules, as well as an improved guide pin retention mechanism that permits guide pins to be inserted into the fiber optic connector following assembly of the fiber optic connector and the polishing of the front face of the ferrule.
Multi-fiber cables or ribbons are being increasingly employed in a wide variety of applications. As such, several standard multi-fiber connectors have been developed and are commonly utilized. Perhaps the most common multi-fiber connector is the MT-RJ connector having a rectangularly-shaped mini-MT ferrule that was developed by Nippon Telegraph and Telephone Corporation of Tokyo, Japan. An MT-RJ connector is commonly assembled utilizing a heat cure epoxy process. In this regard, epoxy is introduced via a window defined by the mini MT ferrule into the bores defined by the MT ferrule through which the end portions of the optical fibers extend. The epoxy is heat cured to secure the end portions of the optical fibers within the mini MT ferrule. The front face of the ferrule is then polished, and the remainder of the components of the MT-RJ connector are assembled about the ferrule.
With respect to the assembly of the other components of the MT-RJ connector, the mini-MT ferrule is mounted within a connector housing such that the front face of the ferrule is exposed. In this regard, the mini-MT ferrule includes a lengthwise extending shank and an enlarged shoulder portion proximate the rearward end of the shank. The shoulder portion is larger in lateral cross-section than the shank, thereby defining a shoulder. Upon insertion of the mini-MT ferrule into the connector housing during the assembly of an MT-RJ connector, the shoulder of the mini-MT ferrule is engaged by an inwardly projecting ledge within the connector housing such that the front face of the ferrule extends outwardly beyond the connector housing while the enlarged shoulder portion of the ferrule is retained within the connector housing. Thus, a mini-MT ferrule must include an enlarged shoulder portion to define a shoulder for engaging the connector housing.
Another common multi-fiber connector is the MT-RJ UniCam(copyright) connector having a modified MT ferrule referred to as the E-ferrule. The UniCam(copyright) connector can be mounted upon one or more optical fibers by means of a mechanical splice that permits the UniCam(copyright) connector to be field installable. In this regard, fiber stubs are typically mounted within respective bores defined by the E-ferrule. The fiber stubs are secured within the ferrule by means of an epoxy, and the front face of the ferrule is then polished. While the mounting of the E-ferrule upon one or more fiber stubs and the polishing of the front face of the ferrule are typically performed at the factory, the UniCam(copyright) connector can be spliced onto one or more field fibers in the field. In this regard, the UniCam(copyright) connector also includes a splice component holder that engages the rearward end of the ferrule. The splice component holder defines a lengthwise extending passageway that is sized and shaped to receive a pair of splice components. The splice components define lengthwise extending grooves for receiving end portions of the optical fiber stubs and the field fibers. In particular, the fiber stubs upon which the ferrule is mounted extend into the grooves defined by the splice components from one end, while the field fibers are inserted into the grooves defined by the splice components from the other end. By rotating a cam member relative to the splice component holder, the splice components are forced together, thereby mechanically splicing the field fibers and the fiber stubs. See, for example, U.S. Pat. No. 6,173,097 by Rodney A. Throckmorton, et al. entitled Field Installable Multifiber Connector, the contents of which are incorporated herein by reference.
Since the E-ferrule must be engaged by the splice component holder in order to ensure alignment of the fiber stubs and the field fibers, the E-ferrule generally has a different design than the MT ferrule utilized by MT-RJ connectors. Rather than an enlarged shoulder, the E-ferrule has a reduced shoulder portion. As such, the portion of the passageway defined by the splice component holder proximate its forward end is sized and shaped to snugly receive the rearward end of the E-ferrule such that the ferrule and the splice component holder are maintained in an aligned relationship.
It would be desirable to provide a common ferrule that is compatible with and capable of replacing both the mini-MT ferrule and the E-ferrule. By providing a common ferrule, the number of different ferrules that would have to be manufactured would be substantially reduced, thereby streamlining manufacturing operations. In addition, the number of different ferrules that would have to be maintained in inventory and carried by field technicians would also be advantageously reduced. Due to the substantial differences in functionality and design of the various ferrules, however, the design of a universal ferrule has been heretofore unsuccessful.
In addition to the MT-RJ connector and the MT-RJ Unicam(copyright) connector, another common multi-fiber connector is the MTP or MPO connector (hereinafter referenced as the MTP connector). The MTP connector has a larger version of the MT ferrule than the MT-RJ connector and can therefore be mounted upon the end portions of a larger number of optical fibers than the MT-RJ connector. As with the MT-RJ connector, however, an MTP connector is commonly assembled by a heat cure epoxy process. In this regard, epoxy is introduced via a window defined by the MT ferrule into the bores defined by the MT ferrule through which the end portions of the optical fibers extend. The epoxy is heat cured to secure the end portions of the optical fibers within the MT ferrule. The front face of the ferrule is then polished, and the remainder of the components of the MTP connector are assembled about the ferrule.
Regardless of the type of multi-fiber connector, the multi-fiber connector should be capable of receiving guide pins in order to facilitate the alignment of the multi-fiber connector with another connector or with an interface device. The alignment of the connector, in turn, permits alignment of the optical fibers upon which the connector is mounted. Depending upon the type of multi-fiber connector, different guide pin retention mechanisms have been developed.
With respect to the MT-RJ and MTP connectors, for example, two different configurations have been developed, namely, a male configuration that includes a pair of guide pins extending outwardly beyond the front face of the MT ferrule and a female configuration that does not include guide pins but that defines a pair of guide pin holes. A pair of these connectors are therefore mated by inserting the guide pins of a male connector into the guide pin holes of a female connector.
In order to retain the guide pins in the male configuration of the MT-RJ or MTP connector, each connector generally includes a pin keeper. During the assembly process, the guide pins are engaged by the pin keeper prior to the insertion of the guide pins into a ferrule. The pin keeper is then positioned immediately rearward of the MT ferrule such that the guide pins inserted through the guide pin holes defined by the MT ferrule from the rear of the MT ferrule so as to protrude outwardly beyond the front face of the MT ferrule. Thus, the guide pins of the male configuration of an MT-RJ or MTP connector must be inserted during the factory assembly process and cannot be inserted in the field once the remainder of the connector has been assembled. As a result, the female configuration of an MT-RJ or MTP connector cannot be converted to a male configuration in the field by merely inserting guide pins through the guide pins holes defined by the MT ferrule since the guide pins will not be appropriately grasped by the pin keeper. Field technicians must therefore maintain an inventory of MT-RJ and/or MTP connectors in both the male configuration and the female configuration since the connectors cannot be converted or otherwise altered in the field.
MT-RJ and MTP connectors also cannot generally be preassembled. Instead, the MT-RJ and MTP connectors must be assembled once the MT ferrule has been mounted upon the optical fibers. In this regard, an MT-RJ and/or an MTP connector cannot be assembled until after the front face of the MT ferrule has been polished since the guide pins of the male configuration of the connector would otherwise protrude beyond the front face of the ferrule and prevent polishing. Additionally, the MT ferrule is typically secured to the optical fibers by means of epoxy injected through a window defined by MT ferrule, thereby also preventing preassembly since the window must remain accessible until the optical fibers have been secured within the MT ferrule. Thus, the MT ferrule is mounted upon a plurality of optical fibers, the front face of the MT ferrule is polished and the remainder of the connector is thereafter assembled.
In contrast to the MT-RJ connector, a UniCam(copyright) connector with an E-ferrule permits the guide pins to be inserted after the front face of the E-ferrule has been polished. In this regard, guide pins can be inserted into corresponding guide pin holes. The guide pins are then glued to the ferrule by means of epoxy injected via the pair of relatively small windows. Unfortunately, the process of gluing the guide pins to the ferrule is a time-consuming operation and must be carefully performed to prevent any epoxy from reaching the front face of the ferrule.
Accordingly while various guide pin retention mechanisms have been developed for multi-fiber connectors, an improved guide pin retention mechanism is desired. In this regard, it would be desirable for a multi-fiber connector to be capable of being converted from a female configuration to a male configuration in the field in order to further reduce the number of different connectors that must be carried by field technicians. As such, it would be desirable for a multi-fiber connector to permit guide pins to be inserted from the front face of the ferrule and engaged by a guide pin retention mechanism following assembly of the multi-fiber connector and polishing of the front face of the ferrule. Additionally, it would be desirable for a multi-fiber connector to include a guide pin retention mechanism that permits guide pins to be inserted and engaged without the use of epoxy or the like.
A fiber optic connector including a multi-fiber ferrule that is compatible with both a mini-MT ferrule and an E-ferrule is therefore provided according to the present invention. Since the multi-fiber ferrule of the present invention is compatible with both types of connectors, the multi-fiber ferrule should reduce the number of different multi-fiber ferrules that must be manufactured and maintained in inventory. Additionally, an improved guide pin retention mechanism is provided by the present invention that is suitable for a variety of different ferrules that permits guide pins to be inserted in the field following assembly of the connector and polishing of the front face of the ferrule, without requiring that the guide pins be adhered to the ferrule by means of epoxy or the like. Thus, a field technician need not carry a stock of both male connectors and female connectors, but can instead carry female connectors and a supply of guide pins in order to convert the female connectors into male connectors, as needed. In order to further facilitate preassembly of the connector, the multi-fiber ferrule may be windowless and the fiber optic connector may be designed to permit epoxy to otherwise be injected into the ferrule following preassembly of the connector without requiring access to a window in the ferrule.
According to one advantageous embodiment, a fiber optic connector is provided that includes a ferrule that is compatible with at least the mini-MT ferrule and the E-ferrule. The ferrule includes a shank defining at least one lengthwise extending bore for receiving an end portion of a respective optical fiber, and a first shoulder portion proximate one end of the shank. The first shoulder portion has a cross-sectional profile that is larger than the shank. As such, the ferrule defines a shoulder for engaging the inwardly projecting ledge of the connector housing of an MT-RJ connector such that the ferrule is compatible with a mini-MT ferrule.
In one advantageous embodiment, the multi-fiber ferrule of the fiber optic connector not only includes the shank and the first shoulder portion, but also a second shoulder portion proximate the first shoulder portion and disposed opposite the shank relative to the first shoulder portion. The second shoulder portion is smaller in lateral cross-section than the first shoulder portion, and generally smaller in lateral cross-section than the shank.
The fiber optic connector of this embodiment can also serve as a UniCam(copyright) connector and, as such, also includes a splice component holder defining a passageway extending lengthwise between opposed first and second ends. The fiber optic connector can also include a plurality of splice components disposed within the passageway defined by the splice component holder for facilitating the mechanical splice of the optical fibers upon which the ferrule is mounted, i.e., the fiber stubs, and a number of other optical fibers, i.e., the field fibers. According to this embodiment, the splice component holder can be designed such that the portion of the passageway proximate the first end of the splice component holder is sized and shaped to snugly receive the second shoulder portion of the ferrule, thereby maintaining the splice component holder and the multi-fiber ferrule in an aligned relationship.
In an alternative embodiment, the ferrule includes the first shoulder portion, but does not include the second shoulder portion. In this embodiment, the first end of the splice component holder engages the first shoulder portion of the ferrule such that the splice component holder and the ferrule are maintained in an aligned relationship as required by a UniCam(copyright) connector. Advantageously, the splice component holder engages the first shoulder portion such that the portions of the splice component holder and the first shoulder portion that are engaged have a combined cross-sectional profile that is no larger than the cross-sectional profile of the first shoulder portion. Thus, the ferrule and splice component holder of this embodiment can be disposed within a conventional connector housing, such as the housing of an MT-RJ connector or a UniCam(copyright) connector.
In order to permit the splice component holder to engage the first shoulder portion of the ferrule, the first shoulder portion of the ferrule can define an opening in communication with the at least one lengthwise extending bore defined by the shank. In this embodiment, the first end of the splice component holder is sized and shaped to be snugly received within the opening defined by the first shoulder portion of the ferrule. Alternatively, the first shoulder portion of the ferrule can define a plurality of lengthwise extending channels. In this alternative embodiment, the first end of the splice component holder can also include a plurality of lengthwise extending tabs for engaging respective channels of the first shoulder portion, thereby maintaining the spliced component holder and the ferrule in an aligned relationship. In any of the foregoing embodiments, however, the multi-fiber ferrule is preferably compatible with a number of conventional ferrules including the mini-MT ferrule and the E-ferrule and, if sized properly, with the MT ferrule.
Regardless of the type of ferrule housed within the fiber optic connector, the fiber optic connector of the present invention also preferably includes a plurality of guide pins. As such, the shank preferably defines a plurality of lengthwise extending holes opening through the front face for receiving respective guide pins. Additionally, the first shoulder portion preferably defines a plurality of lengthwise extending holes in communication with the holes defined by the shank for receiving respective guide pins. However, the second shoulder portion preferably does not define complete holes for receiving respective guide pins. Instead, the plurality of guide pins preferably extend lengthwise beyond the first shoulder portion and along the second shoulder portion. As such, the fiber optic connector can also include a pin retainer for engaging the portions of the plurality of guide pins that extend along the second shoulder portion.
Although the second shoulder portion does not define complete holes for receiving respective guide pins, the second shoulder portion of one advantageous embodiment defines a plurality of lengthwise extending grooves in alignment with the holes defined by the shank and the first shoulder portion for receiving respective guide pins. The grooves defined by the second shoulder portion can be configured in different manners depending upon the design of the ferrule. For example, the plurality of grooves defined by the second shoulder portion can open into an internal opening defined by the second shoulder portion through which the end portions of the optical fibers extend. Alternatively, the plurality of grooves defined by the second shoulder portion can open through an exterior surface of the second shoulder portion.
In embodiments in which the guide pins extend through the internal opening defined by the second shoulder portion, the pin retainer preferably engages the guide pins within the ferrule. In this regard, the pin retainer of one advantageous embodiment includes a body portion extending lengthwise between opposed ends and defining a passageway opening through each of the opposed ends. The body portion is sized to be at least partially and, more preferably, completely received within an internal opening defined by the ferrule. The pin retainer of this embodiment also includes at least one and, more typically, a plurality of engagement members extending laterally outward from the body portion for engaging respective guide pins within the ferrule. For example, the pin retainer typically includes a pair of engagement members extending laterally outward from opposite sides of the body portion. Typically, the plurality engagement members extend laterally outward from a midpoint of the body portion such that the pin retainer is symmetrical about an imaginary plane passing through the plurality of engagement members.
The guide pins typically include circumferential grooves. As such, the pin retainer is preferably designed such that the engagement members can snap within the groove of a respective guide pin as the guide pin is inserted through holes defined by the shank and the first shoulder portion of the ferrule. In order to facilitate the insertion of the engagement members into the circumferential grooves defined by the guide pins, each engagement member can taper laterally outward, if so desired. As such, the guide pins can be advantageously inserted following the assembly of the fiber optic connector and polishing of the front face of the ferrule.
Since the pin retainer is sized and shaped to fit within the ferrule, the combination of the ferrule and the pin retainer is no larger than the ferrule by itself. As such, the ferrule and the pin retainer can be assembled within a conventional connector housing without restricting or otherwise limiting the length or the lateral cross-sectional dimensions of the ferrule.
In embodiments of the fiber optic connector in which the plurality of guide pins extend along an exterior surface of the second shoulder portion, the fiber optic connector can include other types of pin retainers for engaging the guide pins as the guide pins are inserted through the guide pin holes following the assembly of the connector. For example, the fiber optic connector can include a pin retainer defining an opening sized and shaped to receive the second shoulder portion and end portions of the guide pins such that the second shoulder portion can be inserted into the opening defined by the pin retainer. The guide pins will therefore be secured between the pin retainer and the second shoulder portion. In this embodiment, the pin retainer typically includes a plurality of tabs extending into the opening defined by the pin retainer for engaging the circumferential grooves defined by the respective guide pins. In one embodiment, the pin retainer includes a plurality of clips for engaging respective guide pins proximate the second shoulder portion. In this embodiment, the pin retainer can also include a frame connecting the plurality of clips and defining an opening for receiving a second shoulder portion. In both embodiments, however, the pin retainer is preferably no larger in lateral cross-section than the first shoulder portion such that the resulting combination of the ferrule and the pin retainer can be disposed within a conventional connector housing.
A fiber optic connector is therefore provided that includes a common ferrule compatible with at least the mini-MT ferrule and the E-ferrule. Accordingly, use of the ferrule of the present invention would reduce the number of different types of ferrules that must be manufactured and maintained in inventory. Additionally, the fiber optic connector of the present invention includes an improved guide pin retention mechanism that permits guide pins to be inserted following the preassembly of the connector. Thus, the fiber optic connector of the present invention permits guide pins to be inserted in the field in order to convert a female version of a connector to a male version, thereby further reducing the number of different connectors that must be carried by a field technician. Moreover, the fiber optic connector of the present invention permits the end portions of optical fibers to be inserted into and secured within the ferrule and the front face of the ferrule to be thereafter polished following preassembly of the connector since epoxy no longer need be injected through a window defined by the ferrule. In fact, the ferrule can be windowless. Thus, the fiber optic connector of the present invention can advantageously be preassembled.